1. Field of the Invention
The present invention relates to a drive circuit which may be utilized to drive a plurality of capacitive loads independently from each other.
A claim of priority is made to Japanese patent application number 2008-009206, filed Jan. 18, 2008, the subject matter of which is incorporated herein by reference.
2. Description of the Related Art
Drive circuits including a plurality of capacitive loads, and a load drive circuit for driving each of the plurality of capacitive loads independently from each other are generally known. The drive circuits have been used for driving multi-nozzle heads, for example, and are capable of driving a predetermined load only at a predetermined timing.
Japanese Patent Application Laid-Open Publication No. H5-301344, discloses a drive circuit including n circuits of totem-pole type load drive circuits consisting of PNP transistors and NPN transistors. In the disclosed drive circuits, resistors for determining charge time constants or discharge time constants are connected to each of output terminals corresponding to each of the loads. Consequently, the charge time constants or the discharge time constants of the above drive circuit can be individualized at each of the output terminals.
The drive circuits disclosed in the Japanese Patent Application Laid-Open Publication No. H5-301 require resistors for determining the charge time constant or the discharge time constant with respect to each of the loads, and therefore a drawback thereof is that is becomes relatively complicated to determine the charge time constant or the discharge time constant in the case where transistors, capacitors, and resistors, etc., for configuring the drive circuit are integrated on the semiconductor substrates.
In addition, a measurement of connecting external resistors to the loads, etc. as resistors for determining the charge time constant or the discharge time constant is possible as a measure to reduce variations in the charge time constant or the discharge time constant. In the measurement, as the number of the loads to be driven increases, the number of the pins for connecting the external resistors to the circuit including the external resistors and the loads increases, and therefore another drawback arises in that cost reductions and/or the circuit miniaturization are difficult to achieve.